Abstract:

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We report density functional calculations using the full-potential linearized muffin-tin
orbital method on early first row transition metal doped Silicon Carbide in both cubic (3C) and
hexagonal (4H) polytypes. The energy levels in the gap for Ti, V and Cr are in good agreement with
the available photoluminescence experiments. Our calculation shows that the Ti impurity is active
for 4H but not for 3C, while V and Cr impurities are active for both polytypes. The magnetic
interactions are very different for Cr and Mn. Cr shows a very local exchange interaction that decays
rapidly, which is similar for different polytypes and different sites. The exchange interaction for Mn
is quite long range and is very sensitive to the location of the Mn pairs.

Abstract: We used ab initio pseudopotential plane wave methods to study the magnetic and electronic
properties of transition-metal doped ¯-SiC. It is found that the SiC:Cr reveals stable ferromagnetism
with permanent magnetic moments as large as 2 μB regardless of substitution site. In addition, the
SiC:CrSi is predicted to have good electron mobility and wide spin band-gap of 1.58 eV with the
Fermi level at the center of the gap, which is desirable for realizing spintronic devices.

Abstract: Scandium can be used to influence the stoichiometry of SiC during growth of the hexagonal
polytypes. Using PL-EPR and total energy calculations in the framework of density functional
theory, scandium is predicted to be built in predominantly at the Si-sublattice in form of ScSi
acceptors with acceptor levels at 0.55 eV (6H-SiC) and 0.48 eV (4H-SiC). In addition, new PL-EPR
spectra are found with a large anisotropy in the g-tensor suggesting defect pairs as an origin.

Abstract: High concentration of two types of P donors up to 1017 cm-3 in SiC enriched with 30Si
after neutron transmutation doping (NTD) has been achieved. It was established that annealing at
sufficiently low temperature of 1300oC, that is 500-600°C lower compared with annealing of NTD
SiC with natural isotope composition, gives rise to the EPR signal of shallow P donors, labeled sPc1,
sPc2 and sPh. The correlated changes of the EPR spectra of the three sP centres in all the
experiments and the qualitative similarities with spectra of shallow N donors prove that these
centres have shallow donor levels and a similar electronic structure and belong to different lattice
sites. The annealing at 1700°C results in a transformation of one type of P donors (sPc1, sPc2 and
sPh) into another type having low temperature EPR spectra labeled dP.

Abstract: Aluminum-doped 4H-SiC samples were either irradiated with high-energy electrons (170 keV or 1 MeV) or implanted with a box-shaped He+-profile. Admittance spectroscopy (AS) and deep level transient spectroscopy (DLTS) were employed to search for defect centers. AS spectra of as-grown as well as of electron-irradiated (170 keV or 1 MeV) 4H-SiC epilayers reveal the Al acceptor (ΔE(Al) = 200 meV) and an unknown defect (ΔE(SB) = 177 meV), while AS spectra of the He+-implanted and annealed sample show in addition to the Al-acceptor two energetically deeper acceptor-like defect centers (ΔE(RE3) = 255 meV and ΔE(KR3) = 375 meV). The KR3-center is not directly formed by the He+-implantation, it requires an annealing process. The DLTS spectra of the He+-implanted and annealed sample resolve a double-peak structure of the KR3-defect (ΔE(KR3A) = 380 meV and ΔE(KR3B) = 410 meV).

Abstract: 4H-SiC n-channel lateral MOSFETs were manufactured and characterized electrically by current-voltage measurements and by numerical simulation. To describe the observed electrical characteristics of the SiC MOSFETs, Near-Interface Traps (NIT) and mobility degradation models were included in the simulation. The main finding of the simulation is that two models for the NIT states in the upper part of the SiC bandgap are able to describe the electrical data equally well. In one of them, acceptor-like traps and fixed charge are considered while in a newly developed one, donor-like traps are taken into account also.